8 Things to Know About Hair-Smoothing Keratin Treatments

In the pursuit of silky, swingy, frizz-free hair, there are a dizzying number of tempting in-salon hair-smoothing treatments to choose from. We grilled cosmetic chemists and professional hairstylists on what works (and what's safe). Here are the eight things you — and your hair — need to know before you commit.

"Keratin treatment" has become the term of choice for hair-smoothing processes that leave your hair frizz-free for weeks (even months). But forget about the word keratin. "It's just a marketing buzzword; it's not doing anything to smooth the hair," says cosmetic chemist Randy Schueller, editor of thebeautybrains.com.

2. There are, however, several ingredients that can smooth your hair or help it to stay smooth for weeks on end.

First, a quick chemistry lesson: Think of straight hair as a ladder and curly hair as a spiral staircase. The steps on both are the hair's bonds. If you break those bonds, you can rebuild the spiral staircase as a ladder — so curly hair becomes straight. Ammonium thioglycolate and sodium hydroxide permanently break the bonds — that's how traditional relaxers and Japanese straightening treatments transform the texture of the hair. "These treatments last until your hair grows out, but they can be damaging," says Schueller. They can also subject you to a very awkward growing-out phase. Some keratin treatments (and the popular Brazilian Blowout) saturate the hair with a formaldehyde solution before it's dried and flatironed. The formaldehyde (yes, it's a suspected carcinogen for humans) locks the hair into that straighter position so it stays smooth beyond your next shampoo. Your natural texture then gradually returns over two to five months.

3. Just because a stylist or hair-care company says a hair-smoothing treatment is formaldehyde-free, doesn't mean it is.

No hair treatment will technically contain formaldehyde (because — a little more chemistry for you — it's a gas). What they can contain are methylene glycol, formalin, methanal, and methanediol — ingredients that release formaldehyde when heated or mixed with water. Because salon treatments don't require FDA approval, you need to do your own due diligence if you want a formaldehyde-free service. Ask your stylist if the treatment contains formaldehyde (or formaldehyde-releasing ingredients). If they say no, then ask them what exactly will be smoothing your hair. Remember: Keratin (or peptides or silk proteins) is not an acceptable answer. If a treatment is going to defrizz your hair for any length of time, it needs to contain an ingredient that releases the f word or a chemical that permanently breaks the bonds in the hair (see number two). Or it could contain the new smoothing ingredient on the scene.

Several new hair-smoothing treatments — Goldwell Kerasilk, Trissola Solo, Supersilk Smoothing System, and Cezanne Perfect Finish — use glyoxylic acid (or a derivative of it) to lock the hair into a straighter position. There's also the Keratin Complex treatment, which touts itself as a personalized blowout with no downtime, and is celebrating its 10th year. The good news: They're 100 percent formaldehyde-free. The bad news: They're not quite as powerful as the toxic stuff. Results don't usually last more than two or three months, and these treatments won't dramatically soften your curl pattern the way formaldehyde solutions can. "They're not intended to straighten your hair," says hairstylist Nunzio Saviano.

5. Hair-smoothing treatments can be the ticket to a great short haircut.

Have you ever had a stylist talk you out of a pixie? It's not your face shape — it's your frizz. That's why many hairstylists now do a smoothing treatment before a major chop. Henri Borday, the director of education for Cezanne Perfect Finish, says he's even seen an uptick in men coming in for the treatment. If you want to cut your hair short, or already have, look for a salon that does incremental pricing for their smoothing treatments. (You shouldn't pay the same amount as the girl with Sofia Vergara waves in the chair next to you.)

Many brands that make salon smoothing treatments also sell take-home products that they claim will extend your results. Buy them if you want, but don't feel pressured. "Any sulfate-free shampoo will work," says Saviano. Some favorites include the Aveeno Pure Renewal Shampoo, Kevin Murphy's Repair Me Wash, and the

Just don't expect them to last a month. Or even a week (especially if you have tight ringlets). "Most at-home hair-smoothing treatments don't affect any bonds in the hair, so they're not damaging —
or nearly as effective," says Schueller. "They usually just coat the hair shaft with a barrier, like silicone, to keep humidity from entering." In the majority of cases, the only damage you're doing to your hair with these treatments, like Tresemmé 7 Day Keratin Smooth Heat Activated Treatment, comes from hitting it with a flatiron. Results last a week at most — but cost as little as $10. Which is a bargain, considering a typical salon treatment can, and should, cost upwards of $200. "Any salon treatment that costs less than that is worrying, so do your homework," says Saviano. "You're paying for the technician's experience, the time spent on your hair, the credibility of the products, and the proper ventilation. This should not be a walk-in situation." If an in-salon deal looks too good to be true, it probably is.

8. Don't do an in-salon hair-smoothing treatment more than three times a year.

Every time you do one, your hair becomes more brittle and prone to breakage. Unless you're battling life-crippling frizz, save the treatments for when you need them most — like in the summer.